From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yk0-x230.google.com (mail-yk0-x230.google.com [IPv6:2607:f8b0:4002:c07::230]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 9DF5D21FE07 for ; Wed, 26 Aug 2015 22:25:40 -0700 (PDT) Received: by ykll84 with SMTP id l84so9295195ykl.0 for ; Wed, 26 Aug 2015 22:25:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=iC+w14DEN5ugVfaVJjyPWx/n7XLPSnlixPuTax2j2Aw=; b=wHuis2WVg31VecHcLU8ZszHHJnaxC4gGT4bMSKnF2FwCyZPQAtt9vmFvMnZ7rJqWKK i9usi2NGIE8Wt92at2rArsfdRh/xAlpgCTBmpRVOjd3otwgDOCQ+yznkvJErHBSxCSEq C0TNTmN7oU+f1IwzSgj7Hh4OvUUm+h7xlLFWeL07EDgbAC5fkzF96TsV3SISm9LmSDab mNaQGmm2YawPYzqCGVsA6BAe3GsTAn8u3HZEUCeMifuxdCc+BKHW8rL+4WPeET4jH3Mt 20drSRW/SU2ew3FIjX6W6gdLR/MzFbIw1Zw/Jc6G8J6CwstNiNs6nEOWLp7sj9BBHbCb h5eQ== MIME-Version: 1.0 X-Received: by 10.170.95.212 with SMTP id m203mr1937590yka.54.1440653139131; Wed, 26 Aug 2015 22:25:39 -0700 (PDT) Received: by 10.37.49.193 with HTTP; Wed, 26 Aug 2015 22:25:39 -0700 (PDT) Received: by 10.37.49.193 with HTTP; Wed, 26 Aug 2015 22:25:39 -0700 (PDT) In-Reply-To: References: Date: Thu, 27 Aug 2015 08:25:39 +0300 Message-ID: From: Jonathan Morton To: Sebastian Moeller Content-Type: multipart/alternative; boundary=001a11395e929a457e051e443227 Cc: cake@lists.bufferbloat.net Subject: Re: [Cake] Peeling question X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 27 Aug 2015 05:26:02 -0000 --001a11395e929a457e051e443227 Content-Type: text/plain; charset=UTF-8 I'm not *absolutely* sure that the following is correct - I'm extrapolating a little. Except to say that GSO and GRO have zero impact on packet format or size on the wire (unlike jumbo frames). It's entirely reasonable for packets sent with GSO to be received without GRO and vice versa. Of that I am certain. Interfaces that don't support GSO, or where it is turned off, will automatically receive only individual packets. You can examine this capability using ethtool, which works fine on wifi interfaces as well as genuine Ethernet. I haven't tried ethtool on PPP-anything, but I wouldn't expect to see support for offloads there. If for some reason it is there, by all means turn it off. Probably the easiest way to observe GSO in action it to run Codel or fq_codel on the relevant interfaces, without shaping, and put a heavy but simple TCP load, such as nttcp, through it. Watch the maxpacket stat in tc -s qdisc. Some hardware is more aggressive than others. - Jonathan Morton --001a11395e929a457e051e443227 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable

I'm not *absolutely* sure that the following is correct = - I'm extrapolating a little.

Except to say that GSO and GRO have zero impact on packet fo= rmat or size on the wire (unlike jumbo frames).=C2=A0 It's entirely rea= sonable for packets sent with GSO to be received without GRO and vice versa= .=C2=A0 Of that I am certain.

Interfaces that don't support GSO, or where it is turned= off, will automatically receive only individual packets.=C2=A0 You can exa= mine this capability using ethtool, which works fine on wifi interfaces as = well as genuine Ethernet.

I haven't tried ethtool on PPP-anything, but I wouldn= 9;t expect to see support for offloads there.=C2=A0 If for some reason it i= s there, by all means turn it off.

Probably the easiest way to observe GSO in action it to run = Codel or fq_codel on the relevant interfaces, without shaping, and put a he= avy but simple TCP load, such as nttcp, through it.=C2=A0 Watch the maxpack= et stat in tc -s qdisc.=C2=A0 Some hardware is more aggressive than others.=

- Jonathan Morton

--001a11395e929a457e051e443227--